Small Block Crate Engines - Factory Power - Speed Parts Testing

OE manufacturers have always been involved in the performance aftermarket, and today a lot of that involvement centers around producing crate engines, which is smart, considering that so many hot rodders take the easy route in car-building, purchasing a ready-to-run crate engine instead of going through thhe effort of building one themselves.

When we learned that all three OEs had brand-new small-block crate engines, each one supposedly making more than 500 hp and all from totally different schools of thought, we had to investigate and find out what the deal was.

On the plate is a 331 small-block Ford-a little brute built for the pleasures of high-rpm enjoyment. The 440 Mopar small-block (you read that right) is a traditionalist, built to put the torque of cubes into play where a less-endowed 318 or 360 engine would normally be found. Our LSX-based 427 Chevy highlights the awesome potential of a modern engine platform as a substitute for old-school power. While the differences between these engine concepts far outweigh their mechanical similarity, they all share their respective manufacturer's ambition to deliver power to performance-minded people like you and me.

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Ford's 331ci Boss Crate Engine"There's no substitute for cubic inches" is a well-worn expression that's been shouted for years. Well, excuse us for the newsflash, but there are a few substitutes, and on that list is the magic of rpm. In a normally aspirated engine, torque potential falls in a fairly narrow range dependent upon cubic inches. However, horsepower is a factor of two components: torque and rpm. Place torque up the rev range and horsepower will be harvested in abundance- and you'll have no end of fun reaping the benefits.

Nothing is as visceral as an engine that keeps on coming as the tach climbs, making more and more steam as the revs fly up the scale. Some numbers here prove the point. Three hundred eighty six and and a half lb-ft of torque at 5,200 rpm delivers 383 hp, while the same torque at 6,200 rpm dishes up 456 ponies. Kick 386.5 lb-ft of torque out at 7,200 rpm, and you're on the receiving end of 530 hp, the power output we found with this wicked little Ford Windsor crate engine. See how it works?

Putting torque high up the rpm range to make big horsepower isn't as simple as picking a number, or even picking a cam. Actually, making this happen takes a really good engine with a capable selection of parts. The cylinder heads need to have the flow, cross-sectional area, and volume to produce high-rpm power. Ford covered this requirement with a special set of fully CNC'd aluminum heads, PN M-60490-Z304P, which are unique to this 331-cube engine. Ample ports in the heads are critical, but so is an equally suitable intake manifold. Here, Ford specified the Funnelweb, a high-capacity single-plane designed with extended inner runners for a broad torque curve that doesn't quit as the engine winds out. Add a 750 Demon carb and a set of headers (131/44-inch diameter primary at 26-inch length with 3-inch collectors recommended) and you have the airflow system required for high-rpm power.

Naturally, the cam and valvetrain have to be just as suited to the rpm requirement as the airflow system. Ford went with a mechanical flat-tappet camshaft design. Mechanical cams have inherent stability at a high rpm that hydraulics simply cannot match. Ford's choice of lobe profiles carries the ample specifications required to keep the power coming, with 244/252-degrees duration at 0.050-inch tappet rise, and 0.564/0.584-inch lift. Along with the requisite cam specifications, rpm capabilities require a stable and sturdy valvetrain. Meeting the need here are 1.65:1 aluminum roller rockers, hardened pushrods, and a matched dual-spring assembly. Ford's combination worked, showing flawless form in our dyno testing.

If you're looking for high-rpm power, flow capacity and the right cam and valvetrain will get you there, but without attention to durability you've got a time bomb on your hands. Addressing this concern requires bulletproof components throughout, and this Ford is equipped. The foundation for this engine is an M-6010-BOSS302 four-bolt main iron block, filled with an Eagle forged steel crank, Eagle forged rods, and a set of Mahle forged pistons. That's a rugged combination. The 331 cubes are derived from a large bore/short stroke combination measuring 4.125x3.100 inches, in contrast to the more common 4.030x3.250-inch bore and stroke of production block-based strokers of the same displacement. This larger bore and shorter stroke improves the rod ratio, lowers piston speed, and increases breathing area in the bore-all positive steps for high-rpm power and reliability.

The driving force behind developing this engine combination was to capture the legend of classic small-block performance of the past, as exemplified by machines like the AC Cobras or Boss Mustangs. The reality far surpasses the fable of muscle-era powerplants. No small-block powering production or specialty cars back in the '60s or early '70s made this kind of power. Probably few true race small-block engines did, either, and certainly not with the broadly useable and streetable powerband this new Windsor stroker delivers. What Ford accomplished was taking a mythological creature from the past and making it all too real in the present day. Want a turnkey 530hp, 7,200-rpm small-block for your Cobra kit, street Mustang, or retro-rod Falcon? This is your engine.

Mopar's 440ci Super Commando Small-BlockThe Mopar engine we tested makes power via the established path of more cubic inches. While the largest production small-block Mopar measured 360 ci of displacement, this crate engine delivers the same volume as the largest of Chrysler's production big-blocks, at 440 ci. What the cubes do is produce big torque you can feel right off the bottom of the rev range. We observed a torturous 554 lb-ft of torque at 4,300 rpm with the big-inch Mopar small-block, a full 147 lb-ft more, peak-to-peak, than the Ford. That's the power of displacement. Note that the torque peak comes in a full 1,100 rpm lower than the hot Windsor, and therein lies the reason these very different approaches to power create nearly the same peak output-one is a torque motor, the other an rpm piece.

Chrysler small-blocks are far better endowed than those of other manufacturers when seeking to build large displacement. With a 9.60-inch production deck height there is ample room for big stroker cranks, while retaining space for relatively long rods and a reasonable piston compression height. These factors make for solid and reliable stroker combinations, further helped by the Mopar's generous cam-to-crank centerline distance. Common production-engine-based strokers are built to 408 ci using a 4.000-inch-stroke and a cleaned-up 360 bore size of 4.030 inches. The secret to the 440-cube Mopar Performance (MP) crate engine is the use of an MP PN P5153478 siamese-bore block, which takes a 4.180-inch bore size with ease. This block is far sturdier than any production unit, with four-bolt main caps, significant beefing of the main webbing and pan rail, and thicker bores and decks. The rest of the internal engine combination expands on the concept of bulletproof, with a forged 4340 steel crank, forged rods, and forged pistons.

Letting the inches do the work, the Mopar makes use of lower engine speeds, and thus is fitted with a hydraulic flat-tappet camshaft. The hydraulic won't spin over 7,000 rpm, but with ample displacement, there is no reason to go there. Though it is a hydraulic, the specifications on the camshaft are anything but shy, with 251/257 degrees duration at 0.050-inch tappet rise. Valve lift is also ample with 0.603 inch reached through the aid of 1.6:1 ratio shaft-mounted aluminum rocker arms.

One of the highlights of this crate engine package is the all-new aluminum Super Commando cylinder heads. Part of the difficulty in building a big-inch small-block is getting enough cylinder-head capacity for the job. Like most inline valve engines, the Mopar small-block's intake port width is constricted by the factory pushrod location, precluding large ports. With 440 cubes to feed, you're going to be airflow-starved if trying to serve flow through that restricted passage. Mopar realized this way back in the '60s and took advantage of the factory shaft-mounted valvetrain arrangement to offset the intake rockers and pushrods away from the ports, allowing for the much needed port area. From this concept sprang the original offset rocker heads for the small-block Trans Am racing program, followed by a long line of Chrysler's W-series race cylinder heads for the small-block. With the pushrod moved out of the way, there is plenty of room for a straight-shot port, and even more room for porting.

Chrysler's new Super Commando heads feature this offset intake rocker arrangement, greatly increasing the potential output. As fitted to the 440 crate engine, the heads are in raw as-cast form, in contrast to the fully CNC-ported heads of the Ford and Chevy engines tested. The as-cast heads clearly demonstrated their ability to exceed the 500hp mark in our testing, and the potential for dramatic gains above this appear to be a given with a comparable level of port work. Mopar equips the heads with an ample 2.055/1.600-inch valve combination, as the large displacement would demand. The heads are complimented by Mopar Performance's good single-plane M1 intake manifold, and we ensured plenty of flow capacity with the addition of a 1,050-cfm Quick Fuel carb.

With a moderate compression ratio of 10.2:1, this crate engine is set up for no-fuss pump-gas operation. In our dyno session, the burly torque came to bear straight off the bottom, exceeding the 500 lb-ft mark by 3,300 rpm, and breaking the 550 lb-ft barrier by 4,000 rpm. We recorded a power peak of 520 hp at 5,700 rpm, though factory testing has shown 540- plus from this combination. In our test, the Mopar was breathing through small-tube 131/44-Inch headers. An engine of this size would likely benefit in peak power from larger 171/48-inch tubes, as recommended by Mopar Performance, though that tube diameter is not readily available for the Chrysler small-block. With the ability to bring 440 cubes to bear where you'd normally find 318, 340, or 360 inches, this big-inch crate engine would be all too tasty in vintage Mopars, from a stealthy early Valiant to a healthy T/A clone E-body.

GM Performance Parts Iron Block /427 LSXUnlike the other engines tested, our engine from GM is not currently available as a crate engine, but it will be at the end of '08. The good news is that you can easily build this same package with GMPP parts if you can't wait that long. Since its introduction back in 1997, the LS series has been refined and improved by the factory and enthusiastically embraced by the performance crowd. Why? The simple answer is these engines really make some steam. Top dog in production is the LS7, the exclusive 427-cube powerplant found in new Z06 Corvettes. These engines carry a factory rating of 505 SAE net horsepower at 6,300 rpm and 470 lb-ft net torque at 4,800 rpm. That's serious power in anyone's book, especially considering the requirement of production. However, a lot is never enough, right? As racers employed outrageous combinations of displacement, boost, and nitrous, the capabilities of production aluminum blocks reached their limits. GM's answer is the iron LSX block.

The idea behind this block was sheer power-handling capacity, while retaining a price level within the reach of a broad range of racers and street enthusiasts. How much power? These iron blocks were engineered with an eye on output in drag applications in the 2,500hp range! LS-engine architecture is extraordinarily stout, from the six-bolt mains to the heavily reinforced bottom-end bulkheads. The iron LSX block enhances the inherent strength with high tensile iron replacing aluminum, and extra material thickness in critical areas such as the main bulkheads, decks, and cylinder walls. With siamesed cylinder wall castings, the LSX blocks can accept a 4.250-inch bore while retaining 0.200-inch wall thickness. With the bore capabilities and ample room for a 4.250-inch stroke crank, the LSX can easily be built to 482 cubes.

Our test engine is not that extreme in displacement but was built utilizing nearly all production LS7 internals, from a factory steel crank and titanium rods, to the LS7's factory bore and stroke combination of 4.125x4.000 inches. In fact, the only thing that isn't OEM inside is a set of Mahle forged pistons. Up top, this 427-cube powerplant carries a production set of large-port LS7 cylinder heads, which all come beautifully CNC-machined. Interestingly, the LS7 cylinder heads take advantage of the same offset intake rocker strategy as the Mopar engine we tested. A GM Performance Parts single-plane LS7 carbureted intake manifold replaces the factory injection setup, making for an easy retrofit into an earlier chassis. A familiar-looking Holley 950 HP carb provides the mixture without any of the electronic trickery of the injection system.

With a simple intake and four-barrel carb, half the battle is won as far as adapting an LS-based engine to the pre-electronics application of your choice. The other half is dealing with the ignition, since like all LS engines, our test piece fires via a distributorless coil-on-plug ignition. The answer here is from MSD, a simple controller that is designed to work with the OEM sensors, and the late-LS 58x trigger wheel hidden within the crankcase. MSD's controller comes with a harness that literally drops into place to meet the factory connections, requiring only the additional hookup of a power and ground. These control units come preprogrammed with a timing curve, with additional optional plug-in timing curve modules, as well as the ability to hook into a laptop and dial in any timing curve you can dream up. On the dyno, we were impressed by the fact that we just plugged in the MSD and the engine fired nicely to life and idled without doing anything more. For power testing, however, we loaded the MSD software into our laptop and dialed in our own best timing curve.

It's hard to argue with the potential of the LS-based GM engines, especially as the dyno numbers rolled in. With the timing and fuel curves optimized, our LSX iron block 427 registered 552 lb-ft of torque at 5,000-5,200 rpm and 594 hp at 6,400 rpm. With a 1-inch HMV SuperSucker tapered spacer under the carb and the mixture once again optimized, the peak power score rose to 598 hp at the same peak rpm. We were so close to 600 hp we could smell it, but even with a Wilson 2-inch tapered spacer and another round of ignition and fuel tuning, as well as a radius plate above the carb, we stalled at 599 hp at 6,500 rpm. Pretty stout considering the stock LS7 cam reported to be in the engine and the pump gas we were feeding it. It's hard to guess just how much one of these engines could make with a bigger cam and carb (or a big hit of spray), but even as tested it would be a serious piece in the Chevy of your choice-and you'll never have to worry about blowing up the block.